The tobacco industry's role in the 16 Cities Study of secondhand tobacco smoke: do the data support the stated conclusions?

1Cardiovascular Research Institute and Department of Medicine, University of California, San Francisco, California 94143-1390, USA.

Abstract

BACKGROUND:

Since 1996, the tobacco industry has used the 16 Cities Study conclusions that workplace secondhand tobacco smoke (SHS) exposures are lower than home exposures to argue that workplace and other smoking restrictions are unnecessary.

OBJECTIVES:

Our goal was to determine the origins and objectives of the 16 Cities Study through analysis of internal tobacco industry documents and regulatory agency and court records, and to evaluate the validity of the study's conclusions.

RESULTS:

The tobacco industry's purpose in conducting the 16 Cities Study was to develop data showing that workplace SHS exposures were negligible, using these data to stop smoking restrictions by the U.S. Occupational Safety and Health Administration. The extensive involvement of R.J. Reynolds Tobacco Company and the tobacco industry's Center for Indoor Air Research in controlling the study was not fully disclosed. The study's definition of "smoking workplace" included workplaces where smoking was restricted to designated areas or where no smoking was observed. This definition substantially reduced the study's reported average SHS concentrations in "smoking workplaces" because SHS levels in unrestricted smoking workplaces are much greater than in workplaces with designated smoking areas or where no smoking occurred. Stratifying the data by home smoking status and comparing exposures by workplace smoking status, however, indicates that smoke-free workplaces would halve the total SHS exposure of those living with smokers and virtually eliminate SHS exposure for most others.

CONCLUSIONS:

Data in the 16 Cities Study reveal that smoke-free workplaces would dramatically reduce total SHS exposure, providing significant worker and public health benefits.

Effect of smoking policy and practice on the SHS exposures of workers. TWA, time-weighted average. The concentrations of nicotine observed among personal samples collected while at work varied with smoking policy. Smoke-free policies led to much lower concentrations of SHS than policies that restricted smoking to designated areas, but such restrictive policies did reduce SHS concentrations from the levels observed in workplaces without any policies restricting smoking. The categorization by Jenkins et al. (1996) of workplaces that restricted smoking to designated areas as “smoking workplaces” diluted this pool and so substantially reduced the reported SHS concentrations in “smoking workplaces.” Because over half the “smoking workplaces” in fact restricted smoking and the SHS concentrations where smoking was not restricted were > 6 times greater than where they were restricted, the mean reported was half the value that would have been observed had the correct categorization been used (including workplaces that allowed smoking without restrictions). Data from Jenkins and Counts (1999, Table 2).

Daily average concentrations as a function of smoking policies at home and at work. (Smoking workplaces include those that restrict smoking to designated areas.) The 24-hr concentrations are the average of the 8-hr “at work” and the 16-hr “away from work” personal samples. The daily average concentrations increase dramatically for those who live in nonsmoking homes if they work in an environment that “allows smoking” (compare Cell 2 to Cell 1). Those who live in smoking homes also experience a large increase in daily exposures if they also work where smoking is allowed or restricted (compare Cell 4 to Cell 3). Clearly whether or not one works where smoking is allowed has a significant impact on the total daily exposure. Other tobacco specific markers of SHS demonstrate similar relationships. Data from Jenkins et al. (1996, Table 6).